To store and transport flowable materials such as grain, chemicals, fertilizers and minerals, intermediate or semi bulk shipping containers have been developed. These containers are often cylindrical in design and are formed from a flexible woven material. Approximately 1,000 to 3,000 lbs. or more of bulk material may be loaded within the containers which customarily have top loading and bottom discharge features. Flexible intermediate bulk containers are easily transported and stored in an exposed condition and can be readily stacked for high density storage or transportation.
U.S. Pat. No. 4,194,652 describes a flexible intermediate bulk shipping container. A woven container is provided which includes a bottom portion and an upstanding side portion. The side portion is formed from one or more panels sewn together at the vertical edges. The lower edge of the cylindrical side portion is sewn to the periphery of the bottom portion, which includes a discharge spout. A similar spout is situated at the top of the container to facilitate in the loading thereof.
As a result of the inherent properties of flowable or bulk material, a lateral force generated by the bulk material is exerted upon the side wall panels of flexible bulk containers. Flexible circular side walls tend to uniformly distribute the lateral force caused by the bulk material about the containers. However, the lateral force tends to cause a bulging of the container. Bulging is an undesired effect as it distorts the containers causing a loss of storage space when the containers are stacked together. In the extreme, bulging can cause rupture of the container and a spilling of the container's contents. This is especially undesirable when the contents are chemical in composition.
Transportation, be it by truck, train or ship, subjects flexible containers to forces of momentum. Hence, acceleration or deceleration of the transporting vehicle may cause a shifting of the contents of the containers and of the container themselves. To ease some of the problems associated with transportation, flexible intermediate bulk containers have been developed with rigid supporting members.
U.S. Pat. No. 5,025,925 describes a flexible intermediate bulk container flexible container having support pillars associated therewith. The outer surface of the container has vertically placed channels which receive the support pillars. The bottom ends of the support pillars are connected to a wooden pallet. The patent describes that the pillars are useful in reducing strain placed upon the upper end of the forward support pillars and the lower end of the backward support pillars when transport velocity is reduced.
U.S. Pat. No. 4,019,635 describes a tubular cardboard or corrugated board bulk intermediate container which rests within a sleeve that is secured to a bottom pallet. The patent further describes that the relative movement of the container within the sleeve provides for the absorption of a large proportion of the impact energy resulting from transportation of the container.
Because flexible intermediate bulk containers are collapsible, attempts have been undertaken to create self standing side walls to ease in the filling of the container.
U.S. Pat. No. 4,903,859 describes a flexible intermediate bulk container which incorporates rigid panels into the side walls of the container. The patent describes that the rigid panels permit the container to stand alone when filled.
While employing some form of supporting structure, the aforementioned patents do not address or attempt to alleviate the problem of container bulging.
One attempt to overcome the problems associated with bulging involves the placement of flexible containers within a rigid outer cubical frame work structure. Examples of such applications are found in the following patents: U.S. Pat. Nos. 5,437,384; 4,834,255; 4,901,885; 4,927,037; 5,052,579; 5,071,025; 5,282,544; 5,289,937; and 5,407,090. However, this approach is burdensome, expensive and complicated as it requires the construction of an external supporting structure.
It is therefore an object of the present invention to overcome the drawbacks associated with bulging of flexible bulk containers under load. This object is achieved through the use of vertical side beams positioned about the side wall panel of the flexible bulk container.